Multi-Angle Pop-In Mechanical Fastener

ABSTRACT

Pop-in mechanical fasteners having at least one locking tab are described. The locking tab includes a locking surface having a plurality of angled stops.

FIELD

The present disclosure relates to pop-in mechanical fasteners. Themechanical fasteners include a locking surface having at least twoangled stops.

SUMMARY

Briefly, in one aspect, the present disclosure provides a pop-inmechanical fastener comprising a base connected to a pin. The pincomprises an insertion rim and at least one locking tab pivotallyconnected to the insertion rim. The locking tab comprises a wingcomprising an insertion surface and a locking surface comprising a firstangled stop forming a first angle relative to a wing axis, and a secondangled stop forming a second angle relative to the wing axis, whereinthe wing axis is perpendicular to an insertion axis that isperpendicular to the base. Generally the first angle is at least 5degrees and the second angle is greater than the first angle by at least5 degrees.

The following additional features may be included alone or incombination to provide pop-in mechanical fasteners according to variousembodiments of the present disclosure.

In some embodiments, the pop-in mechanical fastener further comprises ashoulder connecting the insertion surface to the locking surface, and aterminal stem extending from the locking surface toward the base.

In some embodiments, the locking surface consists of the first angledstop and the second angled stop. In some embodiments, the lockingsurface further comprises a step between the first angled stop and thesecond angled stop. In some embodiments, the locking surface comprisesthree or more angled stops. In some embodiments, the first angle is atleast 15 degrees, and, in some embodiments, may be no greater than 40degrees. In some embodiments, the second angle is least 25 degrees, and,in some embodiments, may be no greater than 65 degrees. In someembodiments, the first angle is between 20 and 30 degrees, and thesecond angle is between 40 and 50 degrees.

In some embodiments, the insertion surface forms an insertion anglerelative to the insertion axis and the insertion angle is no greaterthan 45 degrees, and, in some embodiments, the insertion angle isbetween 20 and 25 degrees.

In some embodiments, pop-in mechanical fasteners of the presentdisclosure comprise at least three tabs. In some embodiments, at leastone tab is located on the opposite side of the stem from at least oneother tab.

In some embodiments, pop-in mechanical fasteners according to thepresent disclosure, further comprise one half of a mating mechanicalfastener bonded to the base opposite the pin. In some embodiments, thebase of a second pop-in mechanical fastener is bonded to the base of thefirst pop-in mechanical fastener.

In another aspect, the present disclosure provides a pop-in mechanicalfastener comprising a base connected to a pin comprising an insertionrim and at least one locking tab pivotally connected to the insertionrim, wherein the locking tab comprises a wing comprising an insertionsurface and a locking surface comprising an arcuate stop that is concaverelative to the base. In some embodiments, the wing further comprises ashoulder connecting the insertion surface to the locking surface, and aterminal pin extending from the locking surface toward the base. In someembodiments, the locking surface consists of the arcuate stop, while, insome embodiments, the locking surface further comprises as least oneangled stop forming an angle relative to a wing axis, wherein the wingaxis is perpendicular to an insertion axis that is perpendicular to thebase.

In another aspect, the present disclosure provides a method of providinga bonding location on a part comprising providing a pop-in mechanicalfastener according the present disclosure; inserting the insertion rimof the pop-in mechanical fastener into a locking hole in the part,pressing the pop-in mechanical fastener into the hole flexing the tabinto the pin, and further pressing the pop-in mechanical fastener intothe hole until the tabs spring out from the pin and the perimeter of thehole contacts at least a portion of the locking surface of the tab.

The above summary of the present disclosure is not intended to describeeach embodiment of the present invention. The details of one or moreembodiments of the invention are also set forth in the descriptionbelow. Other features, objects, and advantages of the invention will beapparent from the description and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a mating mechanical fastener.

FIG. 2 a illustrates an exemplary pop-in mechanical fastener accordingto some embodiments of the present disclosure.

FIG. 2 b illustrates the insertion of the exemplary pop-in mechanicalfastener of FIG. 2 a into a part.

FIG. 2 c illustrates the deflection of the tabs of exemplary pop-inmechanical fastener of FIG. 2 a as it is further inserted into a part.

FIG. 2 d illustrates the exemplary pop-in mechanical fastener of FIG. 2a after complete insertion into a part.

FIG. 3 a illustrates a prior art locking tab.

FIG. 3 b illustrates the locking surface of the prior art locking tab ofFIG. 3 a.

FIG. 4 a illustrates the interaction of a thick part with the lockingsurface of the prior art locking tab of FIG. 3 b.

FIG. 4 b illustrates the interaction of an intermediate thickness partwith the locking surface of the prior art locking tab of FIG. 3 b.

FIG. 4 c illustrates the interaction of a thin part with the lockingsurface of the prior art locking tab of FIG. 3 b.

FIG. 5 illustrates an exemplary dual-angle locking tab according to someembodiments of the present disclosure.

FIG. 6 a illustrates the interaction of an intermediate to thick partwith the locking surface of the exemplary locking tab of FIG. 5.

FIG. 6 b illustrates the interaction of an intermediate to thin partwith the locking surface of the exemplary locking tab of FIG. 5.

FIG. 7 illustrates an exemplary multi-angle locking tab according tosome embodiments of the present disclosure.

FIG. 8 illustrates another exemplary multi-angle locking tab accordingto some embodiments of the present disclosure.

DETAILED DESCRIPTION

Generally, mating mechanical fasteners such as hook and loop productsand 3M™ DUAL LOCK™ reclosable fasteners provide an alternative toconventional attachment means such as adhesives and welding. Anexemplary mating mechanical fastener is illustrated in FIG. 1. Firsthalf 11 of the mating mechanical fastener includes first base 15, whichis adhered to first part 21, and first stems 13 (e.g., mushroom headedstems). Second half 12 of the mating fastener includes second base 16which is adhered to second part 22, and second stems 17. Generally, thestem designs (e.g., head and stem shapes, spatial distributions, andorientations) of first stems 13 and second stems 17 are selected toachieve the desired interlocking and removal forces when first stems 13are mated with second stems 17 to mechanically couple first part 21 tosecond part 22.

Such mating mechanical fasteners provide an effective means forreleasably and repositionably mechanically coupling one part to another.Generally, the two mating halves of such mating mechanical fasteners areattached to their respective parts prior to connecting the halves tocomplete the mechanical attachment of one part to another. Oftenadhesives are used to attach each half of a mating mechanical fastenerto its respective part such that they remain affixed to their parts asone part is releasably and repositionably connected to another part viathe mating mechanical fastener.

As an alternative to adhering a portion of a mating mechanical fastenerdirectly to a part using adhesives and the like, pop-in mechanicalfasteners have been used to provide an anchoring point to which matingmechanical fasteners can be attached, e.g., adhered. An exemplary pop-inmechanical fastener according to some embodiments of the presentdisclosure is shown in FIGS. 2 a-2 d.

Referring to FIG. 2 a, exemplary pop-in mechanical fastener 100comprises base 140 and pin 105 connected to the base. Pin 105 includesinsertion rim 110, and at least one locking tab 115 extending outwardrelative to insertion axis 101, which is generally perpendicular to base140, although other orientations are possible. Locking tab 115 ispivotally connected to insertion rim 110, and includes wing 120 andterminal stem 130. Wing 120 includes insertion surface 121 and lockingsurface 127.

In some embodiments, the pop-in mechanical fastener includes at leasttwo locking tabs, and in some embodiments, at least three locking tabs.In some embodiments, at least one locking tab, e.g., locking tab 115 a,is positioned on the side of pin 105 opposite at least one other lockingtab, e.g., locking tab 115 b.

Referring to FIG. 2 b, pop-in mechanical fastener 100 can be connectedto part 160 by inserting pin 105 into locking hole 165. After insertionrim 110 has passed through locking hole 165, perimeter 166 of lockinghole 165 encounters insertion surface 121.

Referring to FIG. 2 c, an insertion force is applied to continueinserting pin 105 into locking hole 165. Generally, the insertion forcedepends on the force required to pivot the one or more locking tab(s)115 about insertion rim 110, as the tabs(s) are pressed into the opencenter of pin 105, thereby allowing pin 105 to pass through locking hole165.

Referring to FIG. 2 d, pop-in mechanical fastener 100 is fully insertedwhen base 140 contacts part 160. Generally, the design of pop-inmechanical fastener 100 is selected relative to the dimensions oflocking hole 165 and part 160 such that locking tab 115 springs back outof the center of pin 105. In some embodiments, the perimeter of lockinghole 165 will contact locking surface 127 of wing 120, firmly holdingpop-in mechanical fastener 100 to part 160.

A cross-section of locking tab 315 of the prior art is shown in FIG. 3a. Locking tab 315 includes wing 320 extending from insertion rim 310 toterminal stem 330, which is adjacent base 340 of a pop-in mechanicalfastener. Wing 320 includes insertion surface 321, shoulder 322, andlocking surface 327. Locking surface 327 consists of first angled stop323, second angled stop 325, and step 324 connecting them.

Insertion surface 321 forms an angle, A, relative to insertion axis 301,which is perpendicular to base 340. The greater the angle A, the greaterthe insertion force required when pressing the pop-in mechanicalfastener into place. Also, the greater the angle A, the greater themaximum width, W, of locking tab 315.

Referring to FIG. 3 b, both first angled stop 323 and second angled stop325 form the same angle, B, relative to wing axes 302 a and 302 b, whichare perpendicular to insertion axis 301. The shallower the angle B, thegreater the extraction force required when removing the pop-inmechanical fastener. However, as angle B decreases, the greater thewidth, W, of wing 320 required to provide the same range of height, H1,for first angled stop 323 and height, H2, for second angled stop 325.Furthermore, as the width of wing 320 increases, the greater therequired angle A for a fixed height fastener, leading to an undesirableincrease in insertion force, as described above.

Referring to FIG. 4 a, part 390 a has a thickness, Ta, falling betweendistance 422 and distance 423. When second surface 397 a contacts base340 (i.e., the pop-in mechanical fastener is fully inserted) firstsurface 396 a has passed beyond shoulder 322 and locking tab 315 springsinto place until first surface 396 a engages first angled stop 323,holding part 390 a in place.

Referring to FIG. 4 b, part 390 b has a thickness, Tb, falling betweendistance 423 and distance 424. When second surface 397 b contacts base340, first surface 396 b has passed beyond shoulder 322 and locking tab315 springs into place. Because thickness Tb of part 390 b is less thandistance 423, first surface 396 b does not engage first angled stop 323;rather, locking tab 315 springs outward until step 324 encounters theperimeter of locking hole 365 b. Part 390 b is held in place near base340, but some undesirable movement of perpendicular base 340 can occurequal to the difference between thickness Tb of part 390 b and distance423.

Referring to FIG. 4 c, part 390 c has a thickness, Tc, falling betweendistances 424 and 425. As the pop-in mechanical fastener is pressed intolocking hole 395 c, first surface 396 c passes beyond shoulder 322 andlocking tab 315 begins springing into place. First, the motion of thetab is stopped when step 324 encounters the perimeter of locking hole395 c. Upon the application of additional insertion force, the secondsurface 397 c contacts base 340, and first surface 396 c passes beyondstep 324 allowing locking tab 315 to finish springing into place untiltop first surface 396 c engages second angled stop 325, holding part 390c in place.

The present inventors have identified a variety of deficiencies with apop-in mechanical fastener employing a locking tab of the prior art. Forexample, for certain part thicknesses, significant and undesirablemotion perpendicular to the base can occur. In addition, the presence ofa step between the two angled stops can result in improper insertion asthe tab can stick or hang-up on the step rather than passing on to thesecond angled stop. This can lead to a loose fit, low extraction forces,and even failure. Finally, the use of two angled stops each having thesame angle can limit the range of suitable part thicknesses whilemaintaining an acceptable level of insertion force.

A cross-section of locking tab 515 according to some embodiments of thepresent disclosure is shown in FIG. 5. Locking tab 515 includes wing 520extending from insertion rim 510 to terminal stem 530, which is adjacentbase 540 of a pop-in mechanical fastener. Wing 520 includes insertionsurface 521, shoulder 522, and locking surface 527. Locking surface 527consists of first angled stop 523 and second angled stop 525.

Insertion surface 521 forms an angle, C, relative to insertion axis 501.The greater the angle C, the greater the insertion force required whenpressing the pop-in mechanical fastener into place.

First angled stop 523 forms an angle, D, relative to wing axis 502 a,which is perpendicular to insertion axis 501. Similarly, second angledstop 525 forms an angle, E, relative to wing axis 502 b. The shallowerthe angles D and E, the greater the extraction force required whenremoving the pop-in mechanical fastener. However, as angle D decreases,the greater the width, W, of wing 520 required to provide the same rangeof height, H1, for first angled stop 523. Similarly, although ashallower angle E may be desired to increase the extraction force, asangle E decreases, the greater the width, W, of wing 520 required toprovide the same range of height, H2, for second angled stop 525.Furthermore, as the width of wing 520 increases, the greater therequired angle C for a fixed height fastener, leading to an undesirableincrease in insertion force, as described above.

In some embodiments, angle E is greater than angle D, providing asteeper slope for second angled stop 525. The present inventors havediscovered that for the thinner parts that will engage the second angledstop, a steeper angle still provides an adequately high removal force.In some embodiments, a shallower angle D may be required to maintain anacceptable removal force for the thicker parts that would be held inplace by first angled stop 523. Thus, by combining a steeper angledsecond step and a shallower angled first step, a greater range of partthickness may be accommodated without requiring an undesirable increasein width, W, of wing 520, and the corresponding undesirable increase ininsertion force resulting from an increase in angle C.

Referring to FIG. 6 a, part 590 a has a thickness, Ta, falling betweenmaximum stop height 622 (which in this embodiment corresponds to thepoint of intersection between the first angled stop and the shoulder)and first intermediate stop height 623, which corresponds to the minimumdistance between base 540 and first angled stop 523. When second surface597 a contacts base 540 (i.e., the pop-in mechanical fastener is fullyinserted) first surface 596 a has passed beyond shoulder 522 and lockingtab 515 springs into place until top first surface 596 a engages firstangled stop 523, holding part 590 a firmly in place. Thus, for partshaving a thickness between first intermediate stop height 623 andmaximum stop height 622, the pop-in mechanical fastener is held firmlyin place by first angled stop 523 with substantially no (e.g., no)vertical movement of the fastener.

Referring to FIG. 6 b, part 590 b has a thickness, Tb, falling betweensecond intermediate stop height 624, corresponding to the maximumdistance between base 540 and second angled stop 525, and minimum stopheight 625, corresponding to the minimum distance between base 540 andsecond angled stop 525 (which in this embodiment corresponds to thepoint where the second angled stop intersects the terminal stem). As thepop-in mechanical fastener is pressed into locking hole 595, firstsurface 596 b passes beyond shoulder 522 and locking tab 515 beginsspringing into place.

First, the motion of the tab may be guided by its contact with the firstangled stop. Unlike the prior art locking tab which included a stepbetween the first angled surface and the second angled surface, littleor no additional insertion force is required at the transition betweenfirst angled stop 523 and second angled stop 525. Absent such a stepbetween the first angled stop 523 and second angled stop 525, firstintermediate stop height 623 (which corresponds to the minimum distancebetween the base and the first angled stop) is equal to secondintermediate stop height 624 (which corresponds to the maximum distancebetween the base and the first angled stop). In some embodiments, e.g.,due to variations in manufacturing precision, a slight step may existbetween the first angled stop and the second angled stop. In suchembodiments, the first intermediate stop height will exceed the secondintermediate stop height by an amount equal to the height of the stepbetween them.

When the second surface 597 b contacts base 540, locking tab 515finishes springing into place until first surface 596 b engages secondangled stop 525, holding part 590 b in place.

The range of part thicknesses suitable for use with a particular pop-inmechanical fastener depends in part on the design of the lockingsurface. Specifically, the range of part thicknesses is generally equalto the difference between maximum stop height 622 and minimum stopheight 625. Generally, the actual maximum part thickness and the minimumpart thickness will be affected by the gap between the terminal stem andthe base as well as the height of the terminal stem; however, the rangeof part heights (i.e., the difference between the maximum stop heightand the minimum stop height) will not be affected by these parameters.

Thus, without changing the design of the locking surface and withoutaffecting the range of part heights that can be accommodated, pop-inmechanical fasteners according to the present disclosure can be easilymodified to accommodate different minimum and maximum part heights byadjusting the gap between the terminal stem and the base and/or thelength of the terminal stem. For example, a pop-in mechanical fastenercould be designed to have a locking surface providing a differencebetween the maximum stop height and the minimum stop height of 1.2 mm.By selecting the sum of the gap and the length of the terminal stem tobe 1 mm, such a fastener would accommodate parts ranging in thicknessfrom about 1 mm to about 2.2 mm. By simply selecting the sum of the gapand the length of the terminal stem to be 3 mm, the same fastener designwould accommodate parts ranging in thickness from about 3 mm to about4.2 mm.

Referring to FIG. 2 a, the use of spring tabs 150 may expand the usefulrange of part thicknesses for a particular locking surface design.Generally, spring tabs 150 are pivotally connected to the top surface ofbase 140. Prior to insertion, the spring tabs are angled up away fromthe surface of the base; however, there is a space below the spring tabsallowing the spring tabs to be deflected into the base such that theyare flush with the top surface of the base.

Referring to FIG. 6 b, when the part thickness exceeds minimum stopheight 625, the top of part 590 b will engage locking surface 527 whenthe bottom surface of the part pressed against base 540. However, if thepart thickness were less than the minimum stop height, the top of thepart would be located somewhere below the locking surface, allowing someundesirable vertical motion. By including spring tabs 150, thinner partswill rest on the tops of the spring tabs, which are elevated above thetop surface of the base. Thus these thinner parts will contact thelocking surface and eliminate vertical motion. Because the spring tabscan flex into the base and become flush with the base, the presence ofthe spring tabs does not alter the upper limit of the part thicknessthat can be used. In addition, when the spring tabs are flexed toaccommodate thicker parts, the resistance to bending of the spring tabsmay provide some upward force pressing the part against the lockingsurface, further minimizing any vertical movement.

Although the dual-angle tabs described above are adequate in manysituations, it may be desirable to include more than two angled stops,e.g., three or even four or more angled stops. Taken to the extreme, thelocking surface could include a curved stop having an infinite number ofangled stops. Such embodiments are exemplified in FIGS. 7 and 8, asfollows.

A cross-section of locking tab 715 according to some embodiments of thepresent disclosure is shown in FIG. 7. Locking tab 715 includes wing 720extending from insertion rim 710 to terminal stem 730, which is adjacentbase 740 of a pop-in mechanical fastener. Wing 720 includes insertionsurface 721, shoulder 722, and locking surface 727. Locking surface 727consists of first angled stop 723, second angled stop 725, and thirdangled stop 726.

Insertion surface 721 forms an angle, J, relative to insertion axis 701.The greater the angle J, the greater the insertion force required whenpressing the pop-in mechanical fastener into place.

First angled stop 723 forms an angle, K, relative to wing axis 702 a,which is perpendicular to insertion axis 701. Similarly, second angledstop 725 forms an angle, L, relative to wing axis 702 b, third angledstop 726 forms an angle, M, relative to wing axis 702 c. The shallowerthe angles K, L, and M, the greater the extraction force required whenremoving the pop-in mechanical fastener. However, as the anglesdecrease, the width, W, of wing 720 must increase to provide the samerange of height for each of the respective angled stops. Furthermore, asthe width of wing 720 increases, the greater the required angle J for afixed height fastener, leading to an undesirable increase in insertionforce, as described above.

In some embodiments, angle L is greater than angle K, providing asteeper slope for second angled stop 725. In some embodiments, angle Mis greater than angle L, providing a steeper slope for third angled stop726. In some embodiments, regardless of the number of angled stops, theangle of the stops increases as the stops progress from the shoulder tothe terminal stem of the tab. Referring to FIG. 7, this would result inangle L being greater than angle K, and angle M being greater than angleL. Generally, the present inventors have discovered that for the thinnerparts that will engage the steeper angled stop, a steeper angle providesan adequately high removal force. In some embodiments, shallower anglesmay be required to maintain an acceptable removal force for the thickerparts that would be held in place by the progressively shallower angledstops. Thus, by providing a progression of angled stops, a greater rangeof part thickness may be accommodated without requiring an undesirableincrease in width, W, of wing 720, and the corresponding undesirableincrease in insertion force resulting from an increase in angle J.

This discovery can be extended to a pop-in mechanical fastener having acurved locking surface as illustrated in FIG. 8. Generally, the tangentto any point along the curve defines an angled stop; thus, the curvedsurface could be considered as having an infinite number of angledstops. Although FIG. 8 illustrates a locking surface consisting of asingle curve, locking surfaces combining linear and curved stops, aswell as compound curved locking surfaces may be used.

Referring to FIG. 8, locking tab 815 includes wing 820 extending frominsertion rim 810 to terminal stem 830, which is adjacent base 840 of apop-in mechanical fastener. Wing 820 includes insertion surface 821,shoulder 822, and curved locking surface 827.

Insertion surface 821 forms an angle, P, relative to insertion axis 801.The greater the angle P, the greater the insertion force required whenpressing the pop-in mechanical fastener into place.

Line 803 a is tangent to locking surface 827 near shoulder 822, andforms an angle, Q, relative to wing axis 802 a, which is perpendicularto insertion axis 801. Similarly, line 803 c is tangent to lockingsurface 827 near terminal stem 830, and forms an angle, S, relative towing axis 802 c. An infinite number of tangent lines could be drawnbetween lines 803 a and 803 c, each forming an angle relative to a wingaxis perpendicular to insertion axis 801. For example, line 803 b istangent to locking surface 827 at an arbitrary location between lines803 a and 803 c, and forms an angle, R, relative to wing axis 802 b. Insome embodiments, locking surface 827 is concave, i.e., the angle of aline tangent to locking surface 827 increases along the path of lockingsurface 827 from shoulder 822 to terminal stem 830.

The pop-in mechanical fasteners may be made according to any known meansincluding, e.g., injection molding. The injection mold may be producedusing standard processes to form the desired part design. Generally, thepop-in mechanical fasteners may be formed (e.g., injection molded) fromany suitable material including, e.g., thermoplastic, elastomers,thermoplastic elastomers, curable resins (e.g., thermosetting, moisturecurable, and radiation curable resins), and the like. In someembodiments, materials (e.g., thermoplastic polymers) that exhibit goodelastic recovery properties and tensile strength may be used. In someembodiments, polymers that are relatively insensitive to humidity andhave suitable tensile properties up to 120 degrees C. (° C.) (250degrees F.) may be used. Examples of suitable thermoplastic resins whichmay be used include polypropylene, semicrystalline polymer resins suchas polyolefins and polyolefin copolymers (e.g., based upon monomershaving between 2 and 8 carbon atoms such as polyethylene, polypropylene,ethylene-propylene copolymers, etc.), polyesters, co-polyesters, nylon,polyamides, co-polyamides, fluorinated homopolymers and copolymers,polyalkylene oxides (e.g., polyethylene oxide and polypropylene oxide),ionomers (e.g., ethylene-methacrylic acid copolymers neutralized withbase or salt), cellulose acetate, polyacrylonitrile, polyvinyl chloride,thermoplastic polyurethanes, epoxies (e.g., aromatic epoxies),polycarbonate, amorphous polyesters, amorphous polyamides, ABScopolymers, and polyphenylene oxide alloys. In some embodiments,polypropylene may be preferred.

Generally, once the pop-in mechanical fastener has been formed, it maybe attached to any part having a suitable opening for insertion of thepin. The major surface of the base opposite the pin (i.e., the exposedmajor surface of the base) is then available for any desired useincluding, e.g., attachment of another part via an adhesive.

In some embodiments, one half of a mating mechanical fastener may beattached to the exposed major surface of the base. Suitable methods forattaching the mechanical fastener include adhesives (e.g., pressuresensitive adhesives), ultrasonic bonding, insert molding, and extrusionof a molten polymer layer that bonds the fastener to the based.Generally, it is preferred that the bond of the mating mechanicalfastener to the base is stronger than the pop-in mechanical fastenerdisengagement strength (i.e., the force required to remove (or destroyduring attempted removal of) the pop-in mechanical fastener.

In some embodiments, it may be useful to combine two pop-in mechanicalfasteners of the same or different designs. For example, when bondingtwo parts together, it may be useful to design a first pop-in mechanicalfastener useful over the range of thicknesses typical of the first part.A second pop-in mechanical fastener could them be designed to for useover the typical range of thicknesses for the second part. The bases ofthese two pop-in mechanical fasteners could be bonded to each other,either directly or indirectly (e.g., through the use of adhesives). Inuse, the stem of the first pop-in mechanical fastener would be insertedinto the appropriate hole in the first part, leaving the stem of thesecond pop-in mechanical fastener exposed. Then, an appropriate hole inthe second part could be aligned with the second stem and the secondpart pressed into place being held by the second pop-in mechanicalfastener. By the appropriate selection of base thicknesses, desireddegrees of set-off between the parts could be achieved. Also, throughappropriate design of both pop-in mechanical fasteners, parts over arange of thickness can be held firmly in place with minimal or novertical motion.

Generally, the mechanical fasteners of the present disclosure can beproduced continuously or individually. In some embodiments, the pop-inmechanical fasteners are aligned and fed into a laminator whichlaminates a continuous strip of one half of a mating mechanical fastenerto the exposed major surface of base. The individual pop-in mechanicalfasteners can then be separated into individual pop-in mechanicalfasteners having one half of a mating mechanical fastener attached tothem.

Generally, the dimensions of the various parts of pop-in mechanicalfasteners according to the present disclosure will depend on a number offactors including: the range in thickness of the parts the pop-inmechanical fastener can accommodate and the tolerable dimensions for theholes in the part required to permit insertion of the pins.

Although not limited to the following dimensions, design criteria for aparticular application are described to guide one of ordinary skill inthe art in selecting dimensions. In the automotive industry, themajority of part (e.g., panel) thicknesses varies between 0.70 mm to1.20 mm. Therefore, it may be advantageous for one pop-in mechanicalfastener design to be able to accommodate the entire range of panelthicknesses, yet not exhibit either vertical or sideways movementtypical of current designs. Movement of the mechanical fastener cancause rattle and noise which are unacceptable in, e.g., the automotiveindustry.

Typically, the dimensions of the base are not critical, and can beselected based on well-understood criteria such as surface area requiredfor bonding, mechanical strength, and cost. Generally, the pindimensions will be selected based on additional criteria, as many of thedimensions are interrelated and selection of one dimension (e.g., thewidth of the pin) can limit the selection of other dimensions (e.g., theinsertion angle).

“Total Pin Height” is defined as the distance from the top surface ofthe base to the top edge of the pin. Generally, it is desirable tominimize this dimension due to both cost and space considerations. Forexample, the pin will extend through the hole so there must be adequatespace behind the panel to accommodate the pin. However, the minimumtotal pin height should accommodate the total range of panel thicknesslikely to be encountered. In some embodiments, the total pin height maybe at least five times the maximum intended panel thickness, e.g., atleast six times, or even seven times the maximum panel thickness. Insome embodiments, the total pin height may be no greater than ten times,e.g., no greater than nine times, or even no greater than eight timesthe maximum intended panel thickness. For example, for the automotiveapplication described above, a total pin height of 8 to 9 mm (e.g., 8.55mm) may be used with a maximum intended panel thickness of 1.2 mm.

Generally, the walls of the pin enclose the open center of the pin anddefine the shape of the pin. The pin width is measured parallel to thetabs. The pin thickness is defined as the thickness of the walls of thepin. In some embodiments, the walls of the pin have a constant thicknessalong the height of the pin. In some embodiments, the pin wall istapered near the insertion edge. Generally, a tight fit of the pin inthe hole of the part is desired to prevent or minimize movement.However, it may be desirable to taper the insertion edge so that it iseasier to initiate insertion of the pin in to the hole.

As discussed previously, the width of the tabs depends on at least oneof the following factors, the pin height, the insertion angle, theheights of the angled stops, and the relative angles of the angledstops. In addition, the maximum pin width is affected by the availableopen space within the pin.

The pin width and the pin thickness control the width of the openingwithin the pin, which limits the size of the tabs. Specifically, as thepin is inserted into a hole in a part, the tab(s) are deflected into theopen center of the pin. When the tabs encounter the opposite interiorsurface of the pin, they can no longer flex. Thus, the maximum tab widthis affected by the open area within the pin parallel to the deflectionof the tabs.

The insertion angle may be selected based on, e.g., the pin height, thedesired width of the tabs, the available space for deflection within thepin, and the desired insertion force. In some embodiments, the insertionangle is no greater than 45 degrees, e.g., no greater than 30 degrees,or even no greater than 25 degrees. In some embodiments, the insertionangle is at least 13 degrees, e.g., at least 18 degrees. In someembodiments, the insertion angle is between 20 and 25 degrees, e.g., 23degrees.

Generally, the angle of the first angled stop may be selected based onthe insertion angle, the desired height of the first angled stop, andthe available deflection space within the pin. In some embodiments, thefirst angle is at least 1 degree, e.g., at least 5 degrees, or even atleast 15 degrees. In some embodiments, the first angle is no greaterthan 45 degrees, e.g., no greater than 40 degrees. In some embodimentsthe first angle is between 20 and 30 degrees, e.g., 27 degrees.Similarly, the angle of the second angled stop may be selected based onthe insertion angle, the desired height of the second angled stop, andthe available deflection space within the pin. The second angle isgreater than the first angle, but is less than 90°. In some embodiments,the second angle is greater than the first angle by at least 5 degrees,e.g., at least 10 degrees, or even by at least 20 degrees. In someembodiments, the second angle is at least 25 degrees, e.g., at least 35degrees. In some embodiments, the second angle is no greater than 70degrees, e.g., no greater than 65 degrees. In some embodiments, thesecond angle is between 27 and 65 degrees, e.g., between 40 and 50degrees, e.g., 47 degrees.

The height of the first angled stop is typically selected based on thetotal pin height, the available deflection space within the pin, theangle of the first angled stop and the angle of the second angled stop,and the desired range of part thicknesses. Similarly, the height of thesecond angled stop is typically selected based on the total pin height,the available deflection space within the pin, the angle of the firstangled stop and the angle of the second angled stop, and the desiredrange of part thicknesses.

For the automotive example set forth previously, the height of the firstangled stop may be between 0.25 and 0.35 mm, e.g., 0.31 mm. The heightof the second angled stop may be between 0.75 and 0.9 mm, e.g., between0.8 and 0.85 mm. e.g., 0.82 mm.

Generally, the total height of the angled stops (i.e., the sum of theheights of the first angled stop and the second angled stop) should begreater than the maximum expected part thickness, and sufficient toaccommodate the desired range of part thickness. For the automotiveexample wherein the expected panel thicknesses range from 0.70 to 1.20mm, the total height of the angled stops should span 0.50 mm. Forexample, a total height of 1.13 mm has been shown to cover a range ofpart thickness of 0.65 to 1.30 mm, or a total range of 0.65 mm.

Examples: A pop-in mechanical fastener was designed according to thedimensions set forth in Table 1. The fastener included three tabs withsubstantially identical dimensions. Two tabs were positioned on one sideof the pin and the third tab was position on the opposite side of thepin. This exemplary pop-in mechanical fastener is depicted in FIG. 2 aand the tabs are illustrated in FIG. 5.

TABLE 1 Pop-in mechanical fastener dimensions. Dimension Partdescription (mm) (inch) Base thickness (nominal*) 2.00 0.079 Pin height8.55 0.337 Pin width at the top of the insertion edge 4.22 0.166 Pinwidth at the end of the insertion edge 5.00 0.197 (i.e., at the pivotpoint of the tab) Insertion angle - 23 degrees — — Wing width 3.23 0.127Shoulder height 0.41 0.016 First angled stop Height 0.82 0.032 Width1.61 0.063 Angle - 27 degrees — — Second angled stop Height 0.31 0.012Width 0.29 0.012 Angle - 47 degrees — — Terminal stem height 0.54 0.021Gap between the top of the base and the 0.04 0.002 lower edge of theterminal stem *The base tapers from 2 mm thick below the pin to 1.77 mmat the edges.

Polypropylene resin (PROF-FAX 6523 polypropylene resin obtained fromHimont U.S.A., Inc., Wilmington, Del.) was pigmented with 2 parts ofblack color concentrate (CBK 00010 Black obtained from Clariant Corp.,Charlotte, N.C.) per 100 parts of the polypropylene resin. The pigmentedresin was injection molded per the desired dimensions. Referring to FIG.2 a, grooves 141 in the top surface of base 140 were provided to allowmaterial to flow during the injection molding process used to create thepop-in mechanical fastener. Such grooves may be desirable when formingthe locking tabs for pop-in mechanical fasteners designed for very thinpart thicknesses (e.g., less than 1 mm). Other formation methods orfastener designs may not require such grooves.

One half of a mating mechanical fastener (3M™ Dual Lock™) was attachedto the exposed base of the pop-in mechanical fastener as follows. Theexposed surface of the base of the pop-in mechanical fastener was primedwith 4298UV Promoter (available from 3M Company, St. Paul, Minn.) and a25.4 mm by 26 mm piece of Clear Dual Lock™ SJ3560 (available from 3MCompany) was bonded to the primed surface of the base. Care was taken toinsure adequate/maximum adhesive contact and minimize any airentrapment. The sample was allowed to dwell for about 16 hours at roomtemperature before testing.

Three oval shaped holes were milled into various thickness metal panels.Each hole had a major axis (i.e., a hole length) of 21.5 mm. The minoraxis of the holes (i.e., the hole width) was 5.25 mm, 5.75 mm, and 6.25mm. Generally, thinner panels require narrower width holes to minimizeor prevent both vertical and sideways movement. Thicker panels require awider hole for the tabs to open up. For thicker panels, both verticaland sideways movement are eliminated or minimized by the tabs opening upand catching on the panel.

Generally, with the design of the Example, the minimum panel thicknessfor this was 0.65 mm for a 5.25 mm hole width. This resulted in minimalvertical and sideways movement. As the panel thickness increased to overabout 1.0 mm, the hole width needed to be increased from 5.25 mm to 5.75mm in order for the tabs to clear the hole and snap open upon insertion.The maximum panel thickness was 1.35 mm with a 6.25 mm hole width. Atthis thickness, the panel needed to be moved sideways for the tabs topop open. Extraction performance was expected to be reduced as only asmall amount/area of the tab would catch on the perimeter of the hole.

Insertion and extraction force measurements were conducted using thepop-in mechanical fasteners of the Example, according to the followingtest procedures.

Insertion Force Test Method One half a mating mechanical fastener wasadhered to the exposed surface of the base of a pop-in mechanicalfastener as described in the Example. The second half of the matingmechanical fastener was removably attached to the first half to assistin maintaining the desired orientation of the pop-in mechanical fastenerrelative to the hole during the insertion force test.

With the pin of the pop-in mechanical fastener aligned perpendicular tothe hole of the test panel, the pop-in mechanical fastener was insertedusing a Chatillon tensile tester (Model UTSM, available from JohnChatillon & Sons, New York). The pop-in mechanical fastener was insertedat a rate of about 3.8 cm/minute (1.5 inches/minute) and the peakinsertion force was measured using a Chatillon Digital Force Gauge(Model Number DFGS100) set in its “peak compression mode”.

Fit Test Once the pop-in mechanical fastener was fully inserted in thehole, the relative fit was assessed qualitatively. Both verticalmovement (i.e., movement perpendicular to the part) and horizontalmovement (i.e., movement parallel to the width of the pin) wereassessed. Note that movement parallel to the length of the pin woulddepend on the dimensions of the hole relative to the length dimension ofthe pin, and was not evaluated.

Extraction Force Test Method A hot melt adhesive has applied to a secondhalf of a complimentary mating mechanical fastener (SJ3221 availablefrom 3M). This complimentary half was mechanically engaged with thefirst half of the mating mechanical fastener bonded to the base of thepop-in mechanical fastener. The adhesive firmly held the parts togethersuch that they would not disengage during the extraction test.

The pop-in mechanical fastener was then extracted with the pin alignedwith the hole in the metal test panel at a rate of about 30 cm/min. (12inches/minute) using the Chatillon Tensile Tester and the ChatillonDigital Force Gauge set in its “peak tension mode.” The maximumextraction force was measured and the test termination mode wasrecorded. If peak extraction force occurred when the pop-in mechanicalfastener was removed from the hole, the test termination mode wasrecorded as “Removal.” If the peak extraction force occurred withoutremoving the pop-in mechanical fastener (e.g., an adhesive failed), thetermination mode was recorded as “Destruction.” Regardless of thetermination mode, all samples exhibited an extraction force of at least311 N (70 lbf) and most samples were destroyed rather than being removedat extraction forces exceeding 380 N (85 lbf).

The results of these tests are summarized in Table 2. The reportedvalues are the average of two replicates.

TABLE 2 Test Results Part Insertion Extraction Termination thicknessHole width force Movement force mode 0.71 mm 5.25 mm 46 N (10.3 lbf)minimal 372 N (83.7 lbf) Destruction 0.71 mm 5.75 mm 37 N (8.3 lbf)minimal 380 N (85.1 lbf) Destruction 0.78 mm 5.25 mm 31 N (7.0 lbf) none398 N (89.5 lbf) Destruction 0.87 mm 5.25 mm 57 N (12.8 lbf) none 393 N(88.3 lbf) Destruction 0.98 mm 5.25 mm 36 N (8.2 lbf) none 388 N (87.2lbf) Destruction 1.18 mm 5.75 mm 46 N (10.3 lbf) minimal 316 N (71.1lbf) Destruction/ Removal 1.18 mm 6.25 mm 43 N (9.7 lbf) none 334 N(75.1 lbf) Removal

Various modifications and alterations of this invention will becomeapparent to those skilled in the art without departing from the scopeand spirit of this invention.

1. A pop-in mechanical fastener comprising a base connected to a pincomprising an insertion rim and at least one locking tab pivotallyconnected to the insertion rim, wherein the locking tab comprises a wingcomprising an insertion surface and a locking surface comprising a firstangled stop forming a first angle relative to a wing axis, and a secondangled stop forming a second angle relative to the wing axis, whereinthe wing axis is perpendicular to an insertion axis that isperpendicular to the base, wherein the first angle is at least 5 degreesand the second angle is greater than the first angle by at least 5degrees.
 2. The pop-in mechanical fastener of claim 1, wherein the wingfurther comprises a shoulder connecting the insertion surface to thelocking surface, and a terminal stem extending from the locking surfacetoward the base.
 3. The pop-in mechanical fastener of claim 1, whereinthe first angle is at least 15 degrees and is no greater than 40degrees.
 4. The pop-in mechanical fastener of claim 1, the second angleis least 25 degrees and is no greater than 65 degrees.
 5. The pop-inmechanical fastener of claim 1, wherein the first angle is between 20and 30 degrees, and the second angle is between 40 and 50 degrees. 6.The pop-in mechanical fastener of claim 1, wherein the locking surfaceconsists of the first angled stop and the second angled stop.
 7. Thepop-in mechanical fastener of claim 1, wherein the locking surfacefurther comprises a step between the first angled stop and the secondangled stop.
 8. The pop-in mechanical fastener of claim 1, wherein theinsertion surface forms an insertion angle relative to the insertionaxis and the insertion angle is no greater than 45 degrees.
 9. Thepop-in mechanical fastener of claim 1, wherein the insertion angle isbetween 20 and 25 degrees.
 10. The pop-in mechanical fastener of claim1, wherein the locking surface comprises third angled stop.
 11. Thepop-in mechanical fastener of claim 1, wherein the fastener comprises atleast three tabs.
 12. The pop-in mechanical fastener of claim 11,wherein at least one tab is located on the opposite side of the stemfrom at least one other tab.
 13. The pop-in mechanical fastener of claim1, further comprising one half of a mating mechanical fastener bonded toan exposed major surface of the base opposite the pin.
 14. The pop-inmechanical fastener of claim 1, further comprising a second pop-inmechanical fastener comprising a base and pin, wherein the bases of thepop-in mechanical fasteners are bonded each other.
 15. A pop-inmechanical fastener comprising a base connected to a pin comprising aninsertion rim and at least one locking tab pivotally connected to theinsertion rim, wherein the locking tab comprises a wing comprising aninsertion surface and a locking surface comprising an arcuate stop thatis concave relative to the base.
 16. The pop-in mechanical fastener ofclaim 15, wherein the wing further comprises a shoulder connecting theinsertion surface to the locking surface, and a terminal pin extendingfrom the locking surface toward the base.
 17. The pop-in mechanicalfastener of claim 15, wherein the locking surface further comprises asleast one angled stop forming an angle relative to a wing axis, whereinthe wing axis is perpendicular to an insertion axis that isperpendicular to the base.
 18. A method of providing a bonding locationon a part comprising inserting an insertion rim of a pop-in mechanicalfastener into a locking hole in the part, wherein the pop-in mechanicalfastener comprises a base connected to a pin comprising the insertionrim and at least one locking tab pivotally connected to the insertionrim, wherein the locking tab comprises a wing comprising an insertionsurface and a locking surface comprising a first angled stop forming afirst angle relative to a wing axis, and a second angled stop forming asecond angle relative to the wing axis, wherein the wing axis isperpendicular to an insertion axis that is perpendicular to the base,wherein the first angle is at least 5 degrees and the second angle isgreater than the first angle by at least 5 degrees; pressing the pop-inmechanical fastener into the hole flexing the tab into the pin; andfurther pressing the pop-in mechanical fastener into the hole until thetabs spring out from the pin and the perimeter of the hole contacts atleast a portion of the locking surface of the tab.